# In an infinite multiverse, why is there only one Dark Dimension/Mirror Dimension?

So, I was watching the new Doctor Strange movie (cracking film, by the way) and I realised something odd.

The Ancient One says during an early section, before Strange's training properly starts, that believing in an infinite multiverse also means believing in infinite dangers or something close.

Later on in the film we of course meet the Dark Dimension. It's the Dark Dimension - only one, or so it's implied. But surely, in an infinite multiverse, there will be at least one, if not an infinite number of dimensions/universes in which everything is almost exactly the same, with only small differences, for example the sky is a slightly different colour. Something negligible. So why is there only one Dark Dimension? (For that matter the same thing happens with the Mirror Dimension.

• Plus, infinite copies of infinite dimensions would be a different order of infinity. – Seeds Mar 20 '17 at 20:52
• @Gallifreyan I think Callack means there are infinite numbers between 0 and 1. So there are also a (smaller) infinite number of numbers between 0.506 and 0.507: I.e. more or less 0.506. So if in this analogy 0.506 is the dark dimension there should be infinite universes which as as like the dark dimension as to make no difference – user20310 Mar 20 '17 at 21:07
• Perhaps dimensions and universes are not the same thing. Also, perhaps there actually isn’t an infinite multiverse. This ain’t The Flash! – Paul D. Waite Mar 20 '17 at 23:28
• @Seeds, taking a cross product doesn't increase the order of an infinite set. You have to take a power set to do that. – Harry Johnston Mar 21 '17 at 2:35
• IMO, saying "The" Dark Dimension just means "the particular Dark Dimension that is currently a threat to us". It's like when you talk about "the enemy" you don't necessarily mean they're the only enemy, just the one you're fighting right now. – Harry Johnston Mar 21 '17 at 2:38

In my opinion, it's because universes and dimensions are different: universes are about size, while dimensions are about composition.

Think of a universe as a painting: you can have an infinite number of paintings, all of which are unique; however, they are all 3-dimensional, and every dimension is the same for each of them - what makes a painting different is not more dimensions but its presence or value in each of the dimensions in which it is expressed.

That way, the dark dimension can be infinitely large (every universe can have a dark dimension "value") and yet unique. It also ties in with how it's "invading" our dimension: universes that before had no dark presence now have one and have less "light" presence. The mirror dimension might work similarly.

• This was actually the answer I thought of just as I posted a question. To me it makes the most sense in context so I'm marking it right. Thanks for answering all. – C. R. Yasuo Mar 23 '17 at 17:31

Infinite universes is not the same as every possible universe existing in every possible variation. There are infinite real numbers, but only one of those is zero, and none of them are the square root of -1.

• But an infinite number are almost zero; e.g. 0.00000001 – user20310 Mar 20 '17 at 21:15
• @user20310 - But none of them are almost sqrt(-1). ;) But if you prefer, think of the positive integers, which are also infinite in cardinality, but all at least 1 unit away from zero. – Adamant Mar 20 '17 at 21:16
• Which raises the natural question of whether the multiverse is countable. – eyeballfrog Mar 20 '17 at 23:51
• @eyeballfrog: Not sure it's relevent. If if it is uncountable, they might all still differ from eachother by "at least 1 unit", and then this point stands. – Mooing Duck Mar 21 '17 at 0:00
• @eyeballfrog If you add up all the countable infinite universes you get -1/12. – Ber Mar 21 '17 at 1:32

## Because it's probably the only dark dimension they know about and they have to call it something.

In a universe with an infinite number of dimensions and an infinite number of possible dark dimensions, there is still only one Dark Dimension. The Dark Dimension is the name given to the single dimension containing Dormammu. The name may describe its properties and may be vague enough to match any number of other dimensions, but it's still just the name given to a single unique one.

I'd imagine it's the only dimension of its kind known to The Ancient One, otherwise it'd probably be known by a more descriptive name.